The proposed research will study turbulent and transitional flow patterns, and the effects of drag reducing polymers on these patterns, in certain related medical situations: (1) angiographic injections, (2) flow through subtotal vascular stenoses, and (3) flows in the vicinity of vessel branching, bifurcation, and kinking. In each of these conditions a substantial departure from laminar pulsatile flow prevails; and these deviations are apparently causative agents in creating additional pathologic complications. The turbulence engendered during angiographic injections can create stresses on the vessel wall which promote the probability of dislodging ulcerative lesions, forming emboli distal to the injection site. The fluctuating velocity fields downstream of subtotal vascular stenoses have been strongly linked to poststenotic dilatation. Furthermore, these fields have been demonstrated to be descriptive of the degree of occlusion in the vessel. Flow conditions in the regions of vessel branching and bifurcation have long been suspected culprits in the genesis of atherosclerosis. The research plan is a continuation of a rigorous study of quantitatively defining flow patterns in these situations and a delineation of the effects of drag reducing polymers in suppressing turbulence, altering vessel shear stresses, and augmenting blood flow delivery.